Composite form

ABSTRACT

A composite form for casting concrete slabs combines a relatively thin, inner liner and a relatively thick base plate which are joined by continuous welds so that the two members act as a single unit in resisting bending and shear stresses. By using a relatively thin sheet for the inner liner the bends necessary to provide corners in the finished slab are formed without difficulty while the relatively thick base plate provides the additional strength necessary to keep deflection of the form when it is filled with concrete within acceptable limits.

United States Patent 1 Shoe [451 Oct. 23,1973

[ COMPOSITE FORM [75] Inventor: Theodore William Shoe, Troy, Ohio [73] Assignee: The Flexicore Co., lnc., Dayton,

Ohio

[22] Filed: Mar. 16, 1971 [21] Appl. No.: 124,746

[52] US. Cl. 249/50, 249/99, 249/189,

425/440 [51] Int. Cl. B28b 7/22 [58] Field of Search 249/189, 135, 134,

[56] References Cited UNITED STATES PATENTS 3,023,476 3/1962 Wise 249/135 X 3,618,888 11/1971 Wise ..249/50 Primary ExaminerJ. Spencer Overholser Assistant ExaminerDeWalden W. Jones Attorney-Marechal, Biebel, French & Bugg [57] ABSTRACT Acomposite form for casting concrete slabs combines a relatively thin, inner liner and a relatively thick base plate which are joined by continuous welds so that the two members act as a single unit in resisting bending and shear stresses. By using a relatively thin sheet for the inner liner the bends necessary to provide corners in the finished slab are formed without difficulty while the relatively thick base plate provides the additional strength necessary to keep deflection of the form when it is filled with concrete within acceptable limits.

10 Claims, 5 Drawing Figures Patented Oct. 23, 1973 FIG-2 f VIII 2 Sheets-Sheet 1 INVENTOR THEODORE W. SHQE ATTORNEYS Patented Oct. 23, 1973 2 Sheets-Sheet L1 FIG -3 FIG-5 COMPOSITE FORM BACKGROUND or THE INVENTION Precast concrete structural components, including precast, hollow, floor slabs are now used in constructing a variety of structures such as apartment buildings, factories, etc. One method of forming slabs of this type involves the use of an elongated form of perhaps 60 feet in length and, typically, 2 feet in width. The form has inwardly projecting grout key forming protrusions which form depressions in the lateral edges of the tinished slabs so that when a series of such slabs are laid in edge-to-edge relationship grout may be pumped into the voids formed by these depressions to interlock or key the slabs to each other.

While the use of grout keying depressions in the precast slabs is highly desirable, the provision of such depressions does present some difficulty in stripping the forms from the cured slabs and a number of solutions have been proposed to solve this problem. One solution, which is used on a rather wide scale commercially, is that disclosed in U.S. Pat. No. 3,023,477. As described therein the form is manufactured, essentially, from one piece of high grade steel and the dimensions of the grout key forming means are carefully controlled so that the casting form can be flexed by a special stripping rig to permit the cured slab to be removed from the form. A

While this system has been found highly satisfactory for slabs of, for example, the dimensions noted above, it will be appreciated that if the width of the form is increased considerably, there will be a tendency for the weight of the concrete contained by the form to deflect the form to an unacceptable extent. To combat this one might be inclined to merely increase the thickness of the steel sheet forming the main portion of the. pan. However, as a practical matter, if the thickness of the sheet steel is increased to a point sufficient to resist deflection it becomes too thick to work, particularly to make the sharp bends necessary at the junction of the bottom and side walls of the form. While reinforcing means such as cross beams or the like would also cornbat the tendency towards deflection, it will be apparent that this type of reinforcing would prevent the use of the stripping rig for removing the cured slabs from the form.

U. S. Pat. No. 3,023,476 proposes the use of a rela-- tively thick plate member to which is spot welded a relatively thin sheet of metal which forms the bottom and side walls of the concrete form. The welding of the two sheets may take the form of a series of spot welds down the center thereof or, optionally, along two lines positioned inwardly of the longitudinal edges of the two sheets. With this construction, regardless of the number of lines of spot welds used, there is considerable separation and relative movement between-the sheets as the form is flexed to permit removal of the cured slabs.

This permits concrete and other liquid and solid particles to penetrate and accummulate between the sheets. This penetration and accummulation of undesirable materials is actually increased by the fact that, as a step of the manufacturing process, the form is vibrated after the concrete has been deposited therein. This vibration then increases the penetration of foreign materials between the sheets of steel constituting the form. Eventually, this accummulation will cause buckling of the forms, necessitating rather extensive repairs.

Thus, while it is desirable in many instances to produce extra wide concrete slabs, it will be seen that there is a practical limit to the use of one piece forms for casting such slabs. On the other hand, it will be seen that cross bracing is not acceptable while the use of spot welded plates also presents the difficulties noted above.

SUMMARY OF THE INVENTION The present invention utilizes a relatively thick base plate to which is attached a relatively thin liner having a bottom wall and a pair of upstanding side walls formed integrally therewith and connected thereto by means of smoothly curved fillets. The relatively thin liner is capable of being worked to provide the sharp bends necessary to form the above noted fillets while the relatively thick base plate provides the additional strength necessary to resist deflection and maintain it within acceptable limits.

However, rather than spot welding the two plates and permitting them to move relative to each other, the liner is welded to the base plate by substantially continuous welds extending longitudinally of the liner and base plate at the junction of the bottom and side walls of the liner. Surprisingly, it has been found that by joining the two members at this point they act as a single unit with no observable relative movement between them.

Since there is no relative movement between the plates as they are flexed in the stripping rig a second line of welding can be made along the ends of the two sheets, forming a seal which prevents the penetration of concrete particles, water and other undesirable materials between the base plate and the liner. As a result, the advantages of utilizing a relatively thin, sheet metal member to form the liner are obtained while the relatively thick base plate provides the additional strength necessary to resist deflection.

It should be noted that since the two members act as a single unit, some strength is also gained from the liner itself, thereby rendering it unnecessary to use a base plate of sufficient thickness to provide all of the necessary resistance to deflection.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIGS. 1 and 2 of the drawing, it will be seen that the composite form 10 of the present invention includes a relatively thick base plate 12 and a liner 14 which is relatively thin in comparison to the plate 12. Liner 14 includes a bottom wall 16 and integrally formed, upwardly projecting side walls 18 jointed to the bottom wall 16 by means of smoothly curved fillets 20.

At the point where the bottom wall 16 joins the side walls 18 the liner 14 is attached to the base plate 12 by substantially continuous, longitudinally extending lines of welding 22. Portions of the base plate 12 project outwardly of the two welds 22 and a pair of channel members 24 are mounted on these outwardly projecting portions with their lower flanges 26 attached thereto by continuous strips of welding, as at 28, and a series of plug welds or the like, as at 30.

A pair of grout key strips 32 extend the full length of the form and are attached to the upper edges of the side walls 18 by continuous lines of welding, as at 34. Each of the strips 32 is provided with a series of inwardly projecting protrusions 36 which, in the finished slab, will define a series of depressions. As noted above, when a series of slabs are laid side by side these depressions define grout receptacles which permit adjacent slabs to be locked or keyed to one another. While the grout key forming means are shown as a series of protrusions it will be apparent that a continuous, inwardly projecting strip can also be used as described in the above noted patents.

A spacer bar 38 is interposed between the upstanding web 40 of the channel 24 and the back face of each of the strips 32. This makes the top of the finished slab somewhat narrower than the bottom so that, as noted above, when a series of slabs are laid side by side with their lower edges abutting, a channel is provided for reception of keying grout. Each of the bars 38 may be attached to the strips 32 and the upstanding webs 40 of the channels 24 by a series of welds, as indicated at 42.

Additionally, the channels 24 may be provided with a series of plug welds, as at 44, to further secure the lower edges of the strips 32 and the upper edges of the side walls 18. It will also be seen that the upper edges of the forms are finished by a pair of cap members 46, which are attached to the upper edges of the strips 32 and the upper flanges 48 of the channels 24 by welding,

as at 50 and 52.

While not per se part of the present invention, it will be noted that the forms are also provided with spacer blocks 54 to permit several forms to be stacked for curing. Additionally, bulkhead pins 56 are mounted at each end of the form to permit bulkheads to be attached thereto. While the welds 22 prevent relative movement between the members 12 and 14 it may also be desirable to provide a series of spot welds as indicated at 58 in FIG. 1 of the drawings.

With the above construction it has been found that when the composite form is place in a stripping rig, which may include, as seen in FIG. 3 of the drawings, a contour plate 60 and restraining hooks 62, the form may be flexed upwardly in the center by means of inflatable bags or the like 64 to permit the slab to be removed from the form. During the stripping action the two members 12 and 14 act as a single unit.

Thus, as seen in FIG. 4 of the drawings, if the member 14 alone resists 16,710 psi and the base plate 12, a stress of 38,990 psi, the composite of the members 12 and 14 resists 55,700 psi. It will also be noted that whereas the neutral axis of the member 14 is at the point indicated by the phantom line 66 and that of the base plate 12 is at the point indicated by the phantom line 68, the neutral axis for the composite unit is located at a distance up from the bottom of the plate 12 equal to half the total thickness of the members 12 and 14, as indicated by the solid line 70.

Additionally, since the two members act as a unit, there is no observable relative movement therebetween. As a result, a continuous weld may be made along the edges of the unit, as indicated at 72 of FIGS. 1 and 5 of the drawings and at 74 in FIG. 1 of the drawings. This seals the edges of the unit and prevents the penetration and accumulation of foreign materials therebetween and consequent form deterioration and failure.

In a typical installation for producing a slab approximately 4 feet wide by 60 feet long by 8 inches deep, the base plate 12 would be 7/l6 of an inch thick while the thickness of the liner 14 is less than A that or 3/16 of an inch thick. The fillets connecting the bottom and side walls of the liner are bent at a inch inside radius and continuous welds applied to join the outside of the fillets to the adjacent portions of the upper surface of the base plate 12. With this construction and with the form loaded to approximately 75 pounds per square foot, deflection was measured at approximately Va inch, well within acceptable limits.

From the above it will be apparent that the present invention provides a form which permits the casting of extra wide slabs utilizing presently acceptable slab casting and form stripping techniques and at the same time obviating the draw backs of previous composite type forms.

While the methods herein described, and the forms of apparatus for carrying these methods into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention.

What is claimed is:

l. A composite form comprising:

a. a substantially planar base plate,

b. a substantially U-shaped liner including:

i. a bottom wall positioned in contiguous relationship to said base plate,

ii. side walls projecting away from opposite longitudinal edges of said bottom wall, and

iii. smoothly curved fillets joining said bottom and side walls,

c. grout key forming means projecting inwardly of said U-shaped liner, and

d. a pair of substantially continuous, longitudinally extending welds connecting said liner to said base plate adjacent the juncture of said bottom and sidewalls.

2. The form of claim 1 further comprising:

a. means for preventing the entry of foreign material between said liner and said base plate.

3. The form of claim 1 further comprising:

a. means joining adjacent laterally extending portions of said liner bottom wall and said base plate to prevent the entry of foreign materials therebetween.

4. The form of claim 3 wherein:

a. said joining means comprises substantially continuous welds joining adjacent lateral edges of said base plate and liner bottom wall in sealing relationship to each other.

5. The form of claim 1 wherein:

a. said base plate is substantially thicker than said liner.

6. The form of claim 5 wherein:

a. said base plate is at least twice as thick as said liner.

7. The form of claim 6 wherein:

a. said base plate is approximately 7/16 inch thick,

and

b. said liner is approximately 3/16 inch thick.

8. The form of claim 5 further comprising:

a. means for preventing the entry of foreign materials between said liner and said base plate.

9. The form of claim 8 wherein said last named means comp,ises:

a. a substantially continuous weld joining adjacent, laterally extending edges of said base plate and said liner in sealing relationship to each other.

10. A composite form comprising:

av an elongated, relatively thick, substantially planar,

base plate,

b. an elongated, relatively thin, U-shapecl liner,

c. said liner including integrally formed bottom and side walls joined by smoothly curved fillets,

d. a pair of continuous, longitudinally extending welds joining said liner at said fillets to said base plate with portions of said base plate projecting outwardly from the point of joinder of said base plate and liner,

e. a pair of channels each having upper and lower flanges joined by an upright web,

f. said channels being mounted on said outwardly projecting portions of said base plate with said lower flanges thereof secured to said outwardly projecting portions of said base plate and portions of said web abutting said liner side walls,

g. elongated strips having inwardly prpjecting, grout key forming protrusions,

h. said strips extending in overlying relationship to said webs of said channels with lower edges of said strips secured to upper edges of said liner side walls,

i. spacer bars interposed between said channel webs and said strips adjacent upper edges of said strips, j. cap members secured to said upper flanges of said channels and said upper edges of said strips, and k. continuous, transversely extending welds joining lateral edges of said liner to adjacent portions of said base plate and said webs of said channels. 

1. A composite form comprising: a. a substantially planar base plate, b. a substantially U-shaped liner including: i. a bottom wall positioned in contiguous relationship to said base plate, ii. side walls projecting away from opposite longitudinal edges of said bottom wall, and iii. smoothly curved fillets joining said bottom and side walls, c. grout key forming means projecting inwardly of said U-shaped liner, and d. a pair of substantially continuous, longitudinally extending welds connecting said liner to said base plate adjacent the juncture of said bottom and side walls.
 2. The form of claim 1 further comprising: a. means for preventing the entry of foreign material between said liner and said base plate.
 3. The form of claim 1 further comprising: a. means joining adjacent laterally extending portions of said liner bottom wall and said base plate to prevent the entry of foreign materials therebetween.
 4. The form of claim 3 wherein: a. said joining means comprises substantially continuous welds joining adjacent lateral edges of said base plate and liner bottom wall in sealing relationship to each other.
 5. The form of claim 1 wherein: a. said base plate is substantially thicker than said liner.
 6. The form of claim 5 wherein: a. said base plate is at least twice as thick as said liner.
 7. The form of claim 6 wherein: a. said base plate is approximately 7/16 inch thick, and b. said liner is approximately 3/16 inch thick.
 8. The form of claim 5 further comprising: a. means for preventing the entry of foreign materials between said liner and said base plate.
 9. The form of claim 8 wherein said last named means comprises: a. a substantially continuous weld joining adjacent, laterally extending edges of said base plate and said liner in sealing relationship to each other.
 10. A composite form comprising: a. an elongated, relatively thick, substantially planar, base plate, b. an elongated, relatively thin, U-shaped liner, c. said liner including integrally formed bottom and side walls joined by smoothly curved fillets, d. a pair of continuous, longitudinally extending welds joining said liner at said fillets to said base plate with portions of said base plate projecting outwardly from the point of joinder of said base plate and liner, e. a pair of channels each having upper and lower flanges joined by an upright web, f. said channels being mounted on said outwardly projecting portions of said base plate with said lower flanges thereof secured to said outwardly projecting portions of said base plate and portions of said web abutting said liner side walls, g. elongated strips having inwardly projecting, grout key forming protrusions, h. said strips extending in overlying relationship to said webs of said channels with lower edges of said strips secured to upper edges of said liner side walls, i. spacer bars interposed between said channel webs and said strips adjacent upper edges of said strips, j. cap members secured to said upper flanges of saiD channels and said upper edges of said strips, and k. continuous, transversely extending welds joining lateral edges of said liner to adjacent portions of said base plate and said webs of said channels. 